When to Plant Onions in Chicago: Complete Guide + Best Varieties for Zone 6a

Chicago, Illinois
USDA Zone 6a
Last Frost: May 10
Last updated: October 30, 2025
Learn when to plant onions in Chicago with specific dates for Zone 6a. Compare 6 varieties & discover which grow best in Illinois.
PPatricia "Pat" O'Brien
October 30, 2025
Share:
Chicago gardener planting onion transplants in Zone 6a garden bed in spring

Image © PlantReference.org 2026
Quick Answer
Plant long-day onion varieties in Chicago from mid-April to early May. Plant garlic cloves in October for summer harvest.
TL;DR
Plant onions in Chicago from mid-April to early May using long-day varieties like Allium cepa 'Walla Walla' and Allium cepa 'Red Wing'. Plant garlic cloves in October for summer harvest. Chicago's Zone 6a climate and 42° latitude require strict long-day onion varieties that need 14-16 hours of daylight to form bulbs properly.
NEW PLANT DAILY

Think you know your plants?

Test your botanical knowledge with a new plant identification challenge every day. Build your streak, learn fascinating plant facts, and become a plant identification expert!

Build your streak
One chance per day
Learn as you play

Free account required • Takes less than 30 seconds

Written By
P

Patricia "Pat" O'Brien

Pat has been gardening in Milwaukee for over thirty years, through every kind of Wisconsin weather. She worked as a school librarian and started gardening seriously when her kids were small—she wanted them to know where food came from. Now retired, she's a certified Master Gardener and runs the plant sale at her local garden club every spring. She specializes in cold-hardy perennials, native wildflower meadows, and the art of getting a vegetable garden producing in Wisconsin's short but intense growing season. Pat is practical and patient—she's seen enough Wisconsin winters to know that gardening here is a long game, and she writes with the steady confidence of someone who's been doing this a long time.

Related Plants

Other Articles You May Enjoy